I have a food truck. Is any of this useful?

Yes. The counter app runs on an iPhone, an iPad or an ordinary Android phone or tablet, so a POS for a food truck is one device in somebody's hand. Sales are written on the device first and sent second, so a weak mobile signal does not stop you selling. For receipts, a small Bluetooth printer works from an Android device. From an iPhone or iPad, use a printer on the same wifi, or show the receipt on the screen. Your ordering page takes orders while you are parked.